1. Field of the Invention
The present invention relates to a solid-state imaging apparatus for capturing a one-dimensional optical image input from the outside and a solid-state imaging apparatus for capturing a two-dimensional optical image input from the outside.
2. Related Background Art
Imaging apparatuses such as CCD (Charge Coupled Device) and BBD (Bucket Bridge Device) have been used in various fields such as home video. When electric charges of a photodiode which has a relatively large photosensitive area are handled by a CCD whose charge transfer efficiency is so low that the maximum signal charge amount has to be made small, however, such charges may not completely be transferred therefrom.
Accordingly, among solid-state imaging apparatuses, MOS type image sensors which are not problematic in terms of charge transfer efficiency are used in specific fields. There have been proposals for improving the charge driving speed of the conventional MOS type image sensors, which has been lower than that of CCD. A typical example thereof (simply referred to as "conventional example" hereinafter) is disclosed in N. Ricquier et al., SPIE, Vol. 2172, pp. 2-10.
The MOS type image sensor of the conventional example comprises (a) an area type photosensitive section in which, while M sets of photosensitive pixels each comprising a photodiode for converting an input light signal into a current signal and a switch having a first terminal connected to a signal output terminal of the photodiode and a second terminal for outputting, in response to a vertical scanning signal, the current signal generated at the photodiode are arranged along a first direction (referred to as "vertical direction" hereinafter), N pieces of vertical photosensitive sections each having a signal output terminal electrically connected to the second terminals of the respective switches are arranged along a second direction (referred to as "horizontal direction" hereinafter). Also, this apparatus comprises (b) N pieces of integrating circuits which respectively input the outputs from the N pieces of vertical photosensitive sections and each subject, in response to a reset instruction signal, the current signal output from the vertical photosensitive section to an integrating or non-integrating operation with respect to a capacity element connected between their input and output terminals; (c) N pieces of capacity elements each of which inputs the signal output from the corresponding integrating circuit and outputs an AC component; and (d) N pieces of switches respectively input signals output from the capacity elements and output the signal from a designated capacity element.
This apparatus further comprises (e) a data signal output circuit which selectively inputs, in response to N kinds of horizontal scanning signals, the signals output from the respective capacity elements and outputs an output data signal, while setting, according to an initial voltage setting instruction signal, its input voltage level and output voltage level to a reference voltage, which is their initial level, for a logical true period; and (f) a timing control section for outputting the initial voltage instruction signal, reset instruction signal, N kinds of vertical scanning signals, and N kinds of horizontal scanning signals.
In this apparatus, a light image formed by light input into the area type photosensitive section is captured as follows. First, prior to the execution of a readout operation, the timing control section sets the integrating circuit reset instruction signal to a logical true level, thereby setting the output of the integrating circuit to the reference voltage which is its initial level. Also, before the readout operation is executed, the initial voltage setting instruction signal is set to a logical true level. As a result, the input and output terminals of the data output circuit are set to the reference voltage which is their initial voltage.
Subsequently, the timing control section sets the integrating circuit reset instruction signal and the initial voltage setting instruction signal to logical false levels, and then outputs, as a logical true signal, a vertical scanning signal which turns on only the switch of the first photosensitive pixel in the vertical scanning operation of each vertical photosensitive section. When this switch is turned on, the charge which has been accumulated in the photodiode due to the light received so far is output as a current signal from the photosensitive section. Then, the current signal is instantly accumulated by the integrating circuit into its feedback capacity element and output therefrom as a voltage signal. The signal output from the integrating circuit is input into the capacity element. As a result, the signal input terminal and signal output terminal of the capacity element have a voltage corresponding to the amount of light received in the photosensitive element.
Then, a horizontal scanning signal is set so as to start a readout operation for data concerning the first photosensitive pixel in the vertical direction. The timing control section sets a horizontal scanning signal which instructs only the switch corresponding to the first vertical photosensitive section in the horizontal direction to be selected to a logical true level, thereby turning on only the switch corresponding to the first vertical photosensitive section.
The signal transmitted through this switch is input into the data output circuit and then is output therefrom as an output data signal corresponding to the light amount incident on the first vertical photosensitive section in the horizontal direction. Subsequently, the horizontal scanning signal which instructs only the switch corresponding to the first vertical photosensitive section in the horizontal direction to be selected is set to a logical false level, whereby the data readout operation concerning the first vertical photosensitive section in the horizontal direction is terminated.
Then, as with the first vertical photosensitive section in the horizontal direction, data readout operations for the second and later vertical photosensitive sections are executed. Subsequently, as with the first photosensitive pixel in the vertical scanning operation of each vertical photosensitive section, data readout operations for the second and later vertical photosensitive pixels are executed while, for each time, the timing control section sets the integrating circuit reset instruction signal and initial voltage setting instruction signal to logical true levels so as to set the output of the integrating circuit to its initial level.